Turtle genomic novelty is driven by the evolution of ecological robustness

Turtles are striking among vertebrates in their unique diversity of morphology, ecology, and life-history. A robust physiology is often seen as the primary driver of turtle evolution, and this is increasingly studied in comparative genomics frameworks. Here, we use a genomic-scale dataset from across turtles and a novel comparative method to examine the genomic forces driving evolution in the group. Our approach addresses the correlation structures across species and genes flexibly via Mahalanobis distances from gene-wise pairwise genetic matrices, relaxing the assumption of an overarching species phylogeny. Analysis of outliers in this space reveals that close relatives, notably Cryptodira and Emydidae, share the most accelerated genes, and functional enrichment further indicates that these genes are involved in stress tolerance and immunity. These results reinforce ecological robustness as a core adaptation in turtles, and point to neutral processes as contributing to the genes with accelerated evolution in animals.